Many types of input devices are presently available for performing operations in a computing system, such as buttons or keys, mice, trackballs, joysticks, touch sensor panels, touch screens and the like. Touch screens, in particular, are becoming increasingly popular because of their ease and versatility of operation as well as their declining price. Touch screens can include a touch sensor panel, which can be a clear panel with a touch-sensitive surface, and a display device such as a liquid crystal display (LCD) that can be positioned partially or fully behind the panel so that the touch-sensitive surface can cover at least a portion of the viewable area of the display device. Touch screens can allow a user to perform various functions by touching the touch sensor panel using a finger, stylus or other object at a location often dictated by a user interface (UI) being displayed by the display device. In general, touch screens can recognize a touch event and the position of the touch event on the touch sensor panel, and the computing system can then interpret the touch event in accordance with the display appearing at the time of the touch event, and thereafter can perform one or more actions based on the touch event.
Touch sensor panels typically include a plurality of layers that can be stacked on top of each other. This stackup can include a matrix of drive lines and sense lines formed of a substantially transparent conductive material, such as Indium Tin Oxide (ITO), and a substrate disposed between the drive and sense lines. When the touch sensor panel is used in a bright environment, incident light can hit the interfaces between those layers of the stackup having mismatched refractive indices and can reflect off those interfaces. The light reflected from those interfaces can give rise to the appearance of fringes on the touch sensor panel, which can be visually distracting.